Half Term Blue Moon

Tonight’s a Blue Moon, which happens whenever there are two full moons in a calendar month, although the phrase used to mean the third full moon of a season in which there are four in a quarter-year (or season). A Blue Moon isn’t all that rare an occurence actually. In fact there’s one every two or three years on average. But it does at least provide an excuse to post this again…

Incidentally, today marks the half-way mark in my five-year term as Head of the School of Mathematical and Physical Sciences at the University of Sussex. I started on 1st February 2013, so it’s now been exactly two years and six months. It’s all downhill from here!

I had always thought the term blue moon meant those very rare occasions when the Moon appears slightly blue due to ash particles in the atmosphere after volcanic eruptions or forest fires. Then came the definition of two full moons in the same calendar month, presumably from an American folk tradition, at least to media attention.

This changes the meaning of “once in a blue moon” from an exceptionally rare event to a rather uncommon one. That’s a significant change in meaning.

Literacy varied from place to place and from time to time. Probably only a minority of farmers would have had any formal education, but many could have come across basic education in Sunday schools and adult evening classes.